As well known in the art, PDP is characterized in that it is a thin type, and a large image can be displayed on it. Therefore, PDP is used for business and domestic use, for example, in the form of a wall-hung television set. PDP usually includes a large number of fine discharge display cells. As schematically shown in FIG. 1, each discharge display cell 156 is defined being surrounded by a pair of glass substrates, which are opposed to each other, that is, surrounded by a front glass substrate 161 and a back glass substrate 151, and also surrounded by a fine structural rib 154 which are referred to as a barrier rib or a separation wall. On the front glass substrate 161, there are provided a transparent display electrode 163 formed of a scanning electrode and a maintaining electrode, a transparent dielectric layer 162 and a transparent protective layer 164. On the back glass substrate 151, there are provided an address electrode 153 and a dielectric layer 152. Each discharge display cell 156 has a fluorescent body layer 155 on the inner wall. Further, a rare gas, for example, Ne—Xe gas is enclosed in each discharge display cell 156. Therefore, each discharge display cell 156 can make a display by itself when a plasma discharge is made between the above electrodes. Therefore, light can be emitted from itself. In this connection, to the manufacture of PDP shown in the drawing, it is possible to advantageously apply the present invention which will be explained in detail below. In this connection, PDP rib is commonly made of a fine ceramic structural body and formed into a matrix-shaped pattern or a delta(meandering)-shaped pattern. PDP rib can be advantageously manufactured by using a flexible mold.
In Japanese Unexamined Patent Publication (Kokai) No. 2004-160843, the present inventors has proposed a flexible mold, which is advantageously used for forming PDP ribs, and a manufacturing method of PDP ribs using the flexible mold. According to this invention, a flexible mold having a support body and a shaping layer, which has a groove pattern of a predetermined shape and size on the surface, can be manufactured by the following transfer method which comprises the steps of:
forming a photo-curable material layer upon coating of a photo-curable material at a predetermined film thickness on a metallic mold having a protrusion pattern, the shape and size of which correspond to a groove pattern of the mold;
forming a laminated body of the metallic mold, the photo-curable material layer and a transparent support body by laminating the support body composed of a film of the plastic material on the metallic mold;
curing the photo-curable material layer by irradiating light onto the laminated body from the support body side; and
releasing the resulting shaped layer, which has been formed by curing the photo-curable material layer, from the metallic mold together with the support body.
However, according to the recent investigation by the present inventors, the following matters were found in the method described above. In the case where the flexible mold is manufactured in the way described above, since the photo-curable material is only coated on the metallic mold, air bubbles are incorporated into the resulting photo-curable material layer, and thus it becomes impossible to accurately executing transferring. Especially, in the case of the metallic mold used in this invention, since a larger number of fine protrusions are vertically arranged, when air bubbles are generated in this fine protrusion portion, it is difficult to defoam. Further, it was also found that it is necessary to hold the metallic mold at a high flatness during defoaming and transferring executed after defoaming. That is, when the flatness of the metallic mold is deteriorated, irregularities caused by the deterioration of the flatness are transferred onto the resulting mold as they are and the dimensional accuracy of a distance between ribs is greatly affected.
According to Japanese Unexamined Patent Publication (Kokai) No. 2002-15663, the following method is proposed, as schematically shown in FIG. 2, in the manufacturing of PDP, after a glass substrate 256, on which a dielectric glass paste 255 has been coated, is set on a setting table 253 of a decompressing leveling device 250, a decompressing pump 252 is operated. Due to the operation of the decompressing pump 252, an inner space 254 in a container 251 is put into a decompressed condition. In this patent publication, it is reported that air bubbles 257 existing in the glass paste 255 can be defoamed toward the inner space 254 in the container 251 as shown by the arrow 258 in the drawing. In this method, a whole portion of the glass substrate 256 is covered with the decompressing leveling device 250. In this patent publication, there is no description about the problem that the photo-curable material spreads onto the back side of the metallic mold and the flatness of the metallic mold is deteriorated.
Although it does not propose the manufacture of PDP ribs, Japanese Unexamined Patent Publication (Kokai) No. 2002-187135, as shown in FIG. 3 in order, proposes a method of manufacturing Fresnel's sheets made of silicon resin. First of all, as shown in FIG. 3A, a metallic mold 310 having a pattern corresponding to an objective Fresnel's sheet is prepared. Next, as shown in FIG. 3B, a curable silicone resin 320 is injected onto a metallic mold 310. Further, an aluminum sheet 360 is laminated on it. The silicone resin 320 is subjected to vacuum defoaming and then returned to the atmospheric pressure and hardened at the room temperature. When the silicone resin 320 is peeled off from the metallic mold, the aluminum sheet 360 having the Fresnel's sheet 321 can be obtained as shown in FIG. 3C. In this patent publication, there are no descriptions about the spread of resin and the deformation of the metallic mold, either.